Ultrafast reaction dynamics of the associative hydrogen desorption from Ru(001)

摘要: For a microscopic understanding of chemical reactions at surfaces, it is essential to obtain detailed knowledge on the underlying elementary processes. The reaction mechanism, pathways and timescales energy flow partitioning between different degrees freedom products are key interest. Reactions species adsorbed metal surface generally mediated through electron and/or phonon excitations substrate. Since thermal equilibration these occurs femto- to picosecond timescale, initiated by ultrashort laser pulses provide base investigate processes beyond equilibrium conditions. recombination two hydrogen atoms forming an H2 molecule, which leaves surface, represents one most basic could think thus may serve as prototype system for femtosecond laser-induced chemistry. In particular, Hads+Hads H2,gas associative desorption from Ru(001) has been studied in great detail. Ultrafast transfer times less than 200 fs conjunction with pronounced isotope effect D2 unambiguously indicate hot-substrate electron-driven mechanism. Measurements external (translational) internal (vibrational, rotational) product molecule reveal predominantly translational excitation desorbing hydrogen. Theoretical modelling based multidimensional frictional description ruthenium substrate layer excellently reproduces experimental findings. Furthermore, peculiar characteristics like threshold-like coverage dependence yield promotion effects isotopically substituted adlayers have observed experiment demonstrate importance strong adsorbate–adsorbate interactions H2/D2 association, yet still awaiting quantitative theoretical treatment.